Eccentric drive assemblies generally consist of a crankshaft, and eccentric ball-bearing journaled to the crankshaft, and a connecting rod extending from the bearing. The bearing is constructed of a center hub with an offset hole to receive the crankshaft, and a ring surrounding the hub with the balls separating the two, permitting rotation of one with respect to the other. The rod is secured to the ring, with the result that rotation of the crankshaft will result in reciprocating motion of the connecting rod.
Removal of the bearing for repair and replacement requires disconnecting the drive shaft from its mount and drive mechanisms, and drawing the bearing along the drive shaft in the axial direction to remove it. Additional units positioned on the crankshaft along the way must also be removed. When the drive assembly is the drive for a reciprocating conveyor, it is also necessary to completely remove the entire assembly from the conveyor. Depending on the size of the conveyor and assembly, this will generally require at least two workers, and four to six hours to perform the repair and replacement. When multiple units are driven by a single crankshaft, the need to dismount the crankshaft frequently requires that all such units be disconnected, even if only one needs repair. Overall production costs therefore must include considerable allowances for downtime, man-hours for removal, replacement and repair.
A drive assembly has now been developed which addresses these problems, and provides novel features of independent significance as well. In one aspect, the present invention provides a crankshaft and bearing assembly which permits removal of the bearing in, and replacement from, a direction transverse to the axis of the crankshaft, avoiding the necessity of disengaging the crankshaft from its mount, as well as all other disruptions and disconnections which occur while this is being done. This is accomplished by a crankshaft having an offset journal, in combination with a noneccentric bearing which is split in directions parallel to the crankshaft axis, permitting the bearing to be opened and removed from the journal in a direction transverse to the axis. Secured around the bearing is a housing to which the connecting rod is joined, the housing likewise being split to permit opening and removal in a direction transverse to the crankshaft axis. The split construction and transverse removal capability of the bearing and housing permit both to be removed from the journal without disturbing any other units on the crankshaft, and without demounting or disengaging the crankshaft itself in any manner other than to interrupt the crankshaft rotation. Removal and servicing of the bearing and housing can likewise be performed without disturbing the unit being driven, an example of such unit being a reciprocating conveyor. Roller-type bearings are particularly advantageous as split bearings, since they entail less friction and offer a longer useful life than ball bearings. With the lack of a central hub, the number of parts is reduced, thereby simplifying and reducing maintenance, as well as improving the ability of the operator to inspect bearings for wear.
In another aspect, the assembly is provided with the capability of adjusting the position of the housing and therefore the connecting rod along the axial direction of the crankshaft within a specified range, without disturbing the position of the bearing on the crankshaft. This is accomplished by mating cylindrical surfaces on the bearing and housing, parallel to the bearing bore. The mating surfaces and the contours adjacent to them are configured in such a way that one of these surfaces ca be slid axially along the other prior to the housing being rigidly clamped over the bearing. The clamping mechanism then secures the opposing surfaces against each other at the selected position. This permits an adjustment of the position of the housing along the crankshaft axis without adjustment of the bearing. This is of particular value in aligning the housing or a plurality of housings similarly constructed with the machinery to be driven by the connecting rods.
The preferred housing is one which is split along planes parallel to the bearing bore (and hence the crankshaft axis), to form two arc-shaped parts which when closed encircle the bearing. The cylindrical surface in the housing in these preferred embodiments will therefore consist of two arc-shaped parts which, when joined to the outward-facing cylindrical surface on the bearing exterior completely encircle the bearing except for a slight gap which permits clamping force to be applied. Preferred assemblies will have at least two pairs of mated cylindrical surfaces, while further preferred structures will contain other mated surfaces such as frustoconical surface sections.
Further features, advantages, and embodiments of the invention in each of its aspects will be apparent from the description which follows.